The objective of this program is to better define the process by which iron is transported from the lumen of the gastrointestinal tract to the circulation by the intestinal mucosal cell. Three major phases of this integrated process are being specifically examined. (1) Iron uptake by suspensions of isolated mucosal cells will be used to determine the optimal form of luminal iron for assimilation by the mucosal cell, to characterize the nature of brush border binding of iron, and to assess the effect of prior conditioning of the mucosal cell on iron uptake. (2) Pathways of intracellular iron storage and transport within the mucosal cell will be examined by immunoradiometric assays of ferritin and transferrin in isolated mucosal cells of the rat subjected to various factors known to influence iron assimilation. (3) Studies of iron release and internal regulation of iron absorption have identified that the dog is an appropriate animal model which closely resembles man in regard to the level of dietary iron assimilation and response to variations in iron status. The relationship between serum ferritin and iron absorption is currently being examined in this model. BIBLIOGRAPHIC REFERENCES: Lipschitz, D.A., A. Pollock, M.A. Savin and J.D. Cook: The kinetics of serum ferritin. Clin. Res. 24: 571A, 1976. Lipschitz, D.A. and J.D. Cook: The inhibitory effects of serum on the immunoradiometric assay of ferritin. Proteins of Iron Storage and Transport in Biochemistry. In Press, 1977.